Comparison of five methods of malaria detection in the outpatient setting.

In eastern Africa where 90% of the malaria is due to Plasmodium falciparum, the accuracy of malaria diagnosis at the outpatient level is becoming increasingly important due to problems of drug resistance and use of alternative, costly antimalarial drugs. The quantitative buffy coat (QBC) technique, acridine orange staining with an interference filter system, and the ParaSight-F test have been introduced as alternative methods to conventional microscopy for the diagnosis of malaria. Two hundred thirteen outpatients were tested using these alternative methods and conventional microscopy by five experienced technologists; two were randomly allocated to read the results of each test. Paired results showed the highest level of agreement with the ParaSight-F test (99%), followed by Field stain (92%). The results of the QBC technique showed the least agreement (73%). Using conventional microscopy as the reference standard, the ParaSight-F test had a sensitivity range of 90-92% and a specificity of 99%, staining with acridine orange had a sensitivity range of 77-96% and a specificity range of 81-98% and the QBC technique had a sensitivity range of 88-98% and a specificity range of 58-90%. All microscopic tests showed lower sensitivities (as low as 20% using staining with acridine orange) in detecting low parasitemias (< or = 320/microl) than the ParaSight-F test (70%). Due to the high cost of the ParaSight-F test, Field-stained blood films remain the most appropriate method for diagnosis of P. falciparum in eastern Africa. The ParaSight-F test may be used in situations where no trained microscopists are available, or where malaria is strongly suspected and the results of microscopy are negative.

Response of Plasmodium falciparum to chloroquine and Fansidar in vivo and chloroquine and amodiaquine in vitro in Uganda.

The response of P. falciparum to chloroquine and pyrimethamine-sulfadoxine in vivo and chloroquine and amodiaquine in vitro was investigated in parasitaemic school children from six locations. Mean parasite sensitivity to chloroquine at day 7 was 74% (range 61-97) with parasite clearance rates between 2-3 days and complete defervescence in 85% of febrile children. Sensitivity declined in the four sites followed up to day 14 to 45% (range 37-53). Parasites were significantly more sensitive to pyrimethamine/sulfadoxine at 5/6 sites (100% day 7) but 5% of subjects became parasitaemic by day 14. In vitro isolates were significantly less sensitive to chloroquine than to amodiaquine with a mean 99% effective concentration of 348 mumol/L compared to 6.44 mumol/L. Clearly the role of chloroquine as the primary therapy for uncomplicated P. falciparum malaria should be reconsidered especially in the light of increasing disease severity and resurgence. Amodiaquine may be suitable alternative with pyrimethamine/sulfadoxine as second line and for more severe malaria prior to referral. The cost of alternative antimalarials and the dynamic and deteriorating pattern of resistance are powerful arguments for more objective slide diagnosis to minimise drug pressure and a regular drug sensitivity surveillance system. We believe that the latter should concentrate on measuring clinical drug efficacy in symptomatic outpatients rather than in asymptomatic children while the former needs more pragmatic and economical strategies possibly centred on seasonality and risk.

A comparison of amodiaquine and chloroquine in the treatment therapy of falciparum malaria in Kenya.

During June to August 1989, 158 symptomatic outpatients with P. falciparum malaria were randomly treated with either amodiaquine or chloroquine 25 mg/kg, divided over three days. Amodiaquine (Camoquin, Parke-Davis) was significantly more effective in terms of the rate of parasite clearance, 2.4 versus 3.1 days; parasite clearance day 7; 87% versus 41%; and clinical amelioration, 98% versus 68%. Moreover, this study demonstrates the lack of therapeutic toxicity of amodiaquine. Globally, tolerance was better with amodiaquine than with chloroquine; in particular, cutaneous side effects were less frequent with amodiaquine. There was no evidence of granulocyte or gross hepatic toxicity. These results suggest that WHO recommendations concerning amodiaquine should be questioned. In view of its low cost, demonstrated efficacy and lack of proven therapeutic toxicity, amodiaquine should be considered as a viable replacement for chloroquine in areas with high levels of clinical chloroquine failure.

Comparison of mosquito nets, proguanil hydrochloride, and placebo to prevent malaria.

One hundred and ninety students aged 6 to 18 at a boarding school 120 km west of Nairobi in the Rift Valley participated in a comparative trial of malaria prophylaxis. Treatment with a combination of amodiaquine 25 mg/kg over three days plus doxycycline 100 mg twice daily for five days cleared their blood of Plasmodium falciparum. They were then randomly divided into the following three groups matched for age and sex: one group slept under mosquito nets; one group received one or two tablets (100 mg each) of proguanil hydrochloride daily according to weight; one group received one or two placebo tablets daily which were the same size and colour as the proguanil tablets. Malaria was diagnosed when asexual P falciparum were seen on blood films and was treated with pyrimethamine-sulphadoxine. At the end of one school term 188 of the 190 students had completed the study. One new infection was found during 3893 days of follow up in the mosquito net group, eight new infections over 3667 days in the proguanil group, and 35 new infections over 3677 days in the placebo group, representing a reduction of 97.3% and 77.1% in attack rates for the mosquito net method and for treatment with proguanil respectively. Both provide effective protection from malaria.

Evaluation of the alkaline haematin D-575 method for haemoglobin estimation in east Africa.

In many health facilities in east Africa, haemoglobin estimation is performed using visual colour comparison methods. Efforts to establish colorimetric methods face numerous constraints, including the unavailability of standards for quality control. In contrast, the alkaline haematin D-575 method for haemoglobin estimation is a colorimetric method that uses primary standards prepared from pure, crystalline chlorohaemin. There is no significant difference in the accuracy of the alkaline haematin D-575 method and that of the reference haemiglobincyanide method (P > 0.05), and the response of the alkaline haematin D-575 method is linear for serially diluted blood samples over the haemoglobin concentration range 19.6-3.3 g/dl (r = 0.994, y = 1.01 x - 0.3). The method has a precision of +/-0.3 g/dl (coefficient of variation = (1.8%) for whole blood, and is suitable for use with fixed-wavelength haemglobinometers (lambda = 565 nm) or with colorimeters at lambda = 580 nm. Stable quality control standards could be prepared at provincial, zonal, or reference laboratories and distributed regularly to outlying laboratories.